1. Field of the Invention
This invention relates to a method for processing meat protein and other ingredients to produce a fully-cooked, semi-moist, shelf stable meat product. More particularly, this invention relates to a method comprising a series of pasteurization and mixing steps whereby the resulting fully-cooked meat product, with a taste and texture similar to that of freshly-cooked meat, remains free from pathogen-causing levels of bacteria and can be stored for an extended period of time without refrigeration due to inherent anti-microbial properties.
2. Background of the Invention
Animal meat proteins are a source of quality nutrition in the human diet. Such proteins are desired for their balance of flavor, nutritional value, and serve as the single most complete source of essential amino acids. Meat and meat products have historically been a priority in the diets of most people, but have become increasingly cost prohibitive. As a result, filler ingredients have been added to enhance nutritional quality and lower production costs. Vegetable components can be added to neutralize cholesterol. Fat replacement ingredients, such as starches and flours, can be added to further enhance nutritional quality. Other ingredients can be added to enrich and flavor the resulting products for acceptance within a particular culture. The method and product described herein not only provides a source of protein enrichment having an extended shelf life without refrigeration, but also offers a nutritionally sound product which can be made at cost lower than that of conventional meat protein based products extended by fillers.
In order for meat products to be classified as shelf stable, they must have the ability to be stored for extended periods of time without refrigeration, and without compromising product quality and flavor due to either microbial deterioration, or oxidative reduction. Such meat products must pass government USDA and FDA requirements to obtain a "shelf stable" classification. The principal problem in manufacturing shelf stable meat products is the growth of microorganisms within the nutrient-rich environment of the meat itself. Muscle meats contain approximately 70% water that is available for microbial growth (i.e., unbonded "free" water). In addition, yeasts and molds can effectively exist at even lower water availabilities. To be considered safe for consumption, a practical fully-cooked, shelf stable meat product should be able to inhibit mold and yeast growth, reduce the growth rates of microorganisms already present, and inhibit the growth of new bacteria. Maintaining a favorable taste is also necessary.
The term "semi-moist" shelf stable meat refers to a meat product that is similar in mouth feel and texture to freshly cooked meat, and which exhibits properties that enable the product to resist significant levels of microbial growth when stored without refrigeration for an extended period of time. The product should be further capable of resisting microbial growth when exposed to microorganisms which were not originally present in the product after processing. Microbial proliferation within processed meats depends not only on the amount of moisture available for microorganism growth and nutritive support, but also on the pH of the product, oxygen availability, and proper initial cooking conditions, among other elements. Semi-moist shelf stable meat technology, when fully developed, can be expanded to include multi-component shelf stable products, including meats, beans, legumes, meat salad spreads, chile, burrito/pizza-type food combinations, high calorie protein bars/supplements and meat-flavored cooking ingredients.
Attempts at producing an improved shelf stable meat product include U.S. Pat. No. 3,745,021 issued to Van Middlesworth et. al., which describes a method of pet food manufacture using extrusion cooking of meat trimmings combined with 6-12% water and 3-25% of a mixture containing equal parts of wheat gluten/soy flour and starchy materials to produce a bubbly-textured, non-fibrous, end-product. Increased osmotic pressure created by adding water-soluble sugars to the product is said to limit the amount of unbound water available for supporting microbial growth.
U.S. Pat. No. 4,358,468 issued to Dolan et al. discloses a method of cooking vegetable proteins to produce a pet food that resembles lean meat marbled with fat. Shelf stability of this product is achieved by using unspecified amounts of aqueous solutes. This technology does not, however, utilize meat as the predominant ingredient.
U.S. Pat. No. 5,300,312 issued to Lusas et. al. describes another method of processing vegetable protein with other ingredients by extrusion cooking, after which meat products are added to produce an intermediate moisture vegetable food product resembling meat. This method also requires mechanical drying and re-extrusion to produce the final product. This two-step extruded product utilizes a process and ingredients approved by the FDA, rather than the USDA.
The above-described methods are primarily directed toward producing ready-to-eat foodstuffs from vegetable components by extrusion, using equipment commonly available in the cereal industry. Such equipment is not readily available and/or cost effective for use in the meat industry. In addition, extrusion cooking, while effective, presents at least two problems which obviate their use in the meat industry. First, most extrusion cooking devices are made from ferrous materials, which are not allowed in USDA meat plants. Second, extrusion cooking utilizes high pressures and temperature combinations that require delicate process phase end-point temperature determination measurements. Temperature fluctuations are such that proper evaluation of cooking temperature and monitoring food safety aspects of preparation is very difficult.
There is, therefore, a need to produce a fully-cooked, semi-moist, shelf stable meat product using equipment that is cost-effective, more food-safety oriented and USDA approved. The product should be palatable and flavorful, have meat as the primary ingredient, provide a low initial bacteria count, and serve to inhibit the growth of molds, yeast, and other bacteria. Such a product should serve as a stand-alone source of meat protein, or as a meat cooking ingredient, usable in any application requiring cooked meat.